South America is largely protected from the devastating effects of North Atlantic hurricanes. A tropical cyclone is a rapidly rotating, low-pressure storm system that develops over warm, tropical waters, characterized by a closed atmospheric circulation, strong winds, and thunderstorms. While the continent is not entirely immune to tropical systems, it is generally spared from the direct, intense hurricane landfalls seen in other regions. This geographical anomaly is due to a combination of atmospheric and oceanic factors that actively suppress the formation and track of these massive storms near the South American landmass.
The Geography and Meteorology of Avoidance
The physical location of the continent near the equator is the first barrier against tropical cyclone formation. A fundamental requirement for a hurricane is the Coriolis effect, the force caused by the Earth’s rotation that imparts the necessary spin to organize a storm’s circulation. This rotational force is negligible near the equator, meaning tropical systems rarely develop within five degrees of the equator, encompassing a significant portion of the northern coastline.
A second powerful deterrent is the presence of cold ocean currents along both the eastern and western coasts. Tropical cyclones require sea surface temperatures of at least 26.5°C (80°F) to sustain their structure and intensify. Along the western Pacific coast, the Humboldt Current carries frigid water northward from the Antarctic, keeping sea temperatures too cool for storm development.
A third factor is consistently high vertical wind shear across the tropical latitudes adjacent to the continent. Vertical wind shear is the change in wind speed or direction with increasing altitude, which acts to tilt and disrupt the vertical structure of a developing storm. Strong shear prevents a storm’s heat and moisture from concentrating around its center, effectively tearing apart the fledgling circulation before it can organize into a robust cyclone.
Coastal Regions That See Influence
Despite the meteorological protection, the far northern fringe of South America experiences peripheral effects from North Atlantic hurricanes. Countries like Colombia, Venezuela, Guyana, and Suriname are situated close enough to the main Caribbean hurricane track to feel the residual impacts of passing storms. These regions typically do not face direct landfalls from major hurricanes but are subjected to secondary hazards.
These effects include heavy rainfall, strong gusty winds, and coastal flooding as systems track north of the continent. For example, Hurricane Gilbert in 1988 caused flash flooding in northern Venezuela from its outer rain bands, even though the storm remained offshore.
The probability of a hurricane strike drops dramatically the further south one travels from the Caribbean. South of approximately 10° North latitude, which includes most of the continent, the chance of a direct hit from a North Atlantic system becomes statistically insignificant.
The Phenomenon of South Atlantic Storms
The South Atlantic basin presents a unique meteorological scenario, as it is generally considered hostile to tropical cyclone formation due to high shear and a lack of tropical wave disturbances. This is why the basin remained without a recorded hurricane for centuries, though it occasionally produces weaker tropical or subtropical systems. However, this history was dramatically altered by a singular, powerful event.
In March 2004, the region saw the unprecedented formation of Hurricane Catarina, the only recorded hurricane-strength storm in the South Atlantic. This storm defied the typical climatology and made landfall in the state of Santa Catarina, Brazil, as a Category 2-equivalent hurricane. Catarina’s genesis required a highly unusual alignment of atmospheric variables that temporarily overcame the basin’s typical hostility.
The storm developed when a unique atmospheric blocking pattern reduced the vertical wind shear to an exceptionally low level over a region with marginally warm sea surface temperatures, between 24°C and 26°C. These favorable conditions allowed an extratropical low to slowly transition into a warm-core tropical cyclone, a process virtually nonexistent in this part of the world. Since Catarina, a handful of named tropical and subtropical storms have formed off the coast of Brazil, but the event remains an extreme anomaly that illustrates the difficulty of tropical development in the South Atlantic.